Preparation And Properties Of Composite Nanofiltration Membranes Based On Modified MIL-101(Fe)-NH₂ Materials

As a new type of high-efficiency and energy-saving separation technology,Membrane separation technology has been applied on a large scale,provides an environmentally-friendly and efficienct alternative to traditional water purification technology.Thin-film composite（TFC）membranes represented by nanofiltration and reverse osmosis used the most extensive among membrane separation technology.However,TFC membranes still have shortcomings such as limited to trade-off effect between selectivity and permeability and poor antifouling property.Inorganic nanoparticles are incorporated into the polyamide layer to prepare thin film nanocomposite（TFN）membranes to improve the performance of TFC membranes.There are organic components in the structure of metal-organic frameworks（MOFs）,which have the advantages of precise and adjustable pore size,high porosity and good compatibility with polymers.MOFs material is one kind of ideal TFN membrane fillers.In this research,the polyacrylic acid（PAA）modified MIL-101（Fe）-NH₂ material was loaded on a polysulfone ultrafiltration membrane by self-assembly method,and then prepared a high-performance TFN nanofiltration membrane by interfacial polymerization.To prepare MOFs based TFN membranes needs to synthesize MOFs with good properties.We synthesized the MIL-101（Fe）-NH₂ material by solvothermal method.During the experiment,we found that the material would agglomerate when stored dry,agglomeration would affect the subsequent experiments.Therefore,the material was dispersed in ethanol to prepare MIL-101（Fe）-NH₂ ethanol dispersion.The material was characterized by SEM,TEM and XRD,results shows that the synthesis of MIL-101（Fe）-NH₂ was successful.The MIL-101（Fe）-NH₂ material is reacted with PAA to synthesize MIL-101（Fe）-NH₂@PAA material.Characterized by TEM,FTIR and XRD.Results shows that the surface of the modified MIL-101（Fe）-NH₂@PAA material was coated with PAA,and the hydrophilicity and dispersibility were significantly enhanced.This research separates the surface deposition of MIL-101（Fe）-NH₂@PAA material and interface polymerization process,could control and optimize the two processes separately.The MIL-101（Fe）-NH₂@PAA material was deposited on the polysulfone ultrafiltration membrane by self-assembly method to prepare the MIL-101（Fe）-NH₂@PAA composite membrane.The surface material of the membrane material is evenly distributed,forming a dense MIL-101（Fe）-NH₂@PAA composite layer,which significantly improve the hydrophilicity of polysulfone membrane.MIL-101（Fe）-NH₂@PAA TFN nanofiltration membrane was prepared by the interfacial polymerization reaction.The morphology,roughness,hydrophilicity and surface potential of the nanofiltration membrane were researched by water contact angle measurement,Zeta potential measurement,XPS,SEM,FTIR and AFM etc.The permeability and anti-fouling performance of the membrane were studied through cross-flow filtration equipment,CLSM and fluorescence in situ hybridization.The results shows that the pure water flux of MIL-101（Fe）-NH₂@PAA TFN nanofiltration membrane reaches 8.15 L/m²·h at 25℃and 0.7 MPa,and the rejection rates for Mg SO₄ and Na Cl reaches 98%and 90%,respectively.the flux recovery rate of BSA under long-term antifouling test reaches 98.1%,MIL-101（Fe）-NH₂@PAA TFN nanofiltration membrane has good permeability and antifouling performance.